1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a semiconductor device using an aligner.
2. Description of the Related Art
Conventionally, photolithography technology is indispensable when manufacturing a semiconductor device. Exposure is executed on a photoresist under this photolithography technology. When this exposure is executed, plural wafers in an aligner are considered as one lot. Then, an alignment correction value is calculated every lot in the aligner, and the exposure is executed while correcting alignment based on this alignment correction value.
FIG. 12 is a flow chart showing a method for calculating an alignment correction value based on a prior art. In this prior art, first, one wafer is arbitrarily selected as a pilot from one lot, and the exposure of this wafer is executed (Step S1). Next, an amount of misalignment of this pilot is calculated, and a decision is made if this amount is within tolerance or not (Step S2). If the amount of misalignment is found within the tolerance by this decision, other wafers in this lot are exposed without correcting alignment (Step S3). If the amount of misalignment is found over the tolerance, both an alignment correction based on this amount of misalignment and regeneration of the wafer used as the pilot are executed (Step S4). Then, the exposure of this pilot is executed again (Step S1).
As another method, a trend of misalignment in the lot already exposed is found out before another lot is exposed, and then, the exposure is executed by correcting the alignment based on this trend.
As a further method, the exposure is executed by fixing the alignment correction value of the aligner.
A prior art is disclosed in Japanese Patent Laid-open Publication number Hei 07-167614.
However, it is difficult to execute the accurate correction when using the method for correcting based on the trend of misalignment and the method for fixing the alignment correction value. Especially, errors of the correction have become beyond the limit of what is acceptable due to recent miniaturization. On the other hand, it is possible to thoroughly correct the alignment when using the method for calculating the alignment correction value by extracting the pilot. However, problems of long time for a series of processes and high costs arise.